1. Field of the Invention
This invention relates to sealants and more particularly relates to sealants which are useful in glazing applications.
2. Brief Description of the Prior Art
Kunkle in U.S. Pat. No. 2,974,377 discloses a vulcanizable sealant composition suitable for use in multiple glazing applications comprising butyl rubber blended with polyisobutylene or polybutene and cured with para-dinitrobenzene. This is an excellent sealant for use in multiple glazed units providing a hermetic seal. Unfortunately, the sealant composition, even before curing, has an extremely high viscosity or consistency due to the relatively high proportion of butyl rubber in comparison to the polybutene or polyisobutylene. This high viscosity usually requires high milling or extruding temperatures, which activate the curing agent and vulcanize the sealant composition in the mill or extruder. When it is desired to utilize the vulcanized composition for sealing multiple glazed window units, high temperature and pressure equipment such as high temperature, long barrel extruders to extrude the sealant into bead or ribbon form must be used. This type of extrusion equipment is very expensive, usually cannot be afforded by the small window fabricator and cannot be used in the field to extrude the sealant in usable form for glazing multi-pane window units. In addition, after the sealant is extruded into ribbon form, its viscosity or consistency is such that it does not readily cold flow and the sealant must be applied to the multiple glazed window unit with pressure clamps and rigid spacers. These latter disadvantages make field applications impractical and also increase the expense of fabricating for the small manufacturer.
From the above, it is apparent that what is needed is a sealant composition which has a relatively low viscosity so that the components of the sealant can be extruded together at low temperatures without activating the curing agent, thereby providing an uncured low viscosity sealant composition which can be used with low temperature and pressure equipment. The low viscosity sealant composition once applied to the multiple glazed unit should vulcanize while in place preferably at room temperature to form a hermetic seal. This invention provides such a sealant.